The Irvine Police Department has released the identity of the man accused of shooting and killing a UPS driver in his truck on Thursday, and it appears the two men worked together.

According to a release from police, Rhean Fontanoza, 46, was the attacker who pulled up alongside Expedito Cuesta De Leon, 50, at Chrysler and Bendix streets in Irvine at about 3 p.m.

De Leon was declared dead at the scene.

Fontanoza, meanwhile, was located about an hour later and eventually arrested after a standoff with a SWAT team.

A motive for the attack has not been disclosed, but both men are from Aliso Viejo, and “it appears Fontanoza and De Leon were acquaintances,” police said.

It later emerged that Fontanoza is also a UPS employee, prompting a statement from the company.

“We are shocked and saddened by the latest developments in Irvine, CA. These are highly unusual circumstances and do not represent the culture of our company and the camaraderie among our employees around the world,” a spokesperson said. “Our focus now is on supporting our people and their loved ones during this extremely difficult time. Since the investigation is ongoing, we defer any additional questions to the investigating authorities.”

Anyone with information is asked to call Detective Craig Voors at 949-724-7131 or email cvoors@cityofirvine.org.